Vehicle seat comprising load sensor and side frame having a concave part

ABSTRACT

A vehicle seat includes a load sensor that is configured to measure a load applied from an occupant and that has a rod extending therefrom, a seat cushion frame that includes right and left side frames that extend along a front-rear axis, and a bracket member attaching the load sensor to at least one of the right and left side frames. A lower surface of the at least one side frame has a concave part opening downward. At least a part of the load sensor is lower than the concave part, and the load sensor is closer to a center of the vehicle seat than the concave part.

This is a Continuation of U.S. application Ser. No. 13/137,173 filed Sep. 7, 2011, which is a Continuation of U.S. application Ser. No. 12/875,594 filed Sep. 3, 2010, which is a Continuation of U.S. application Ser. No. 11/992,548 filed Mar. 25, 2008, which is a National Stage of International Application No. PCT/JP2006/319477 filed Sep. 29, 2006, which in turn claims the benefit of priority from Japanese Application No. 2005-286881 filed Sep. 30, 2005. The disclosures of the prior applications are hereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a passenger's weight measurement device for a vehicle seat, which measures a weight of a passenger seated on the vehicle seat, and to an attachment structure for attaching a load sensor to the passenger's weight measurement device.

BACKGROUND ART

In recent years, in some cases, operations of various safety devices such as a seat belt and an air bag have been controlled in accordance with a weight of a passenger seated on a vehicle seat for the purpose of enhancing performance of the safety devices. In a conventional passenger's weight measurement device that measures the weight of the seated passenger, a load sensor is interposed between a vehicle floor and the vehicle seat (for example, refer to Patent Document 1 and Patent Document 2).

-   Patent Document 1: JP A H8-164039 -   Patent Document 2: JP A H9-207638

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, there is a dimension error or an assembling position error when the passenger's weight measurement device is assembled, when the vehicle seat is fixed to the passenger's weight measurement device or when the passenger's weight measurement device is fixed to the vehicle floor, or the like. Accordingly, it has been difficult to assemble the passenger's weight measurement device.

In this connection, it is an object of the present invention to provide a passenger's weight measurement device for a vehicle seat, which is more easily assembled, and to provide an attachment structure for a load sensor.

Means for Solving the Problems

In order to solve the above-described problem, a passenger's weight measurement device for a vehicle seat according to the present invention comprises: an upper rail provided on a lower rail fixed to a vehicle floor so as to be movable in a rear and front direction; a load sensor fixed onto the upper rail; and a frame provided on the load sensor and below the vehicle seat, wherein a rod is extended from the load sensor, the rod sequentially penetrates the frame and a spring holder and is inserted into a coil spring, a nut is screwed to the rod from above the spring holder, and the coil spring is sandwiched between the spring holder and the frame and is compressed by tightening the nut to the spring holder.

An attachment structure for a load sensor according to the present invention is an attachment structure for attaching the load sensor to a frame provided below a vehicle seat, wherein a rod is extended from the load sensor, the rod sequentially penetrates the frame and a spring holder and is inserted into a coil spring, a nut is screwed to the rod from above the spring holder, and the coil spring is sandwiched between the spring holder and the frame and is compressed by tightening the nut to the spring holder.

In the present invention, preferably, the spring holder includes a cup portion in which a through hole through which the rod penetrates is formed in a bottom, and a flange formed on an outer circumference of the cup portion, and the cup portion is inserted through the coil spring, the nut is inserted into the cup portion to tighten the bottom of the cup portion, and the coil spring is sandwiched between the flange and the flame.

In the present invention, preferably, a collar through which the rod is inserted penetrates the frame, the spring holder is sandwiched between the collar and the nut, and the coil spring and the collar are sandwiched between the nut and the load sensor.

In accordance with the present invention, the nut is screwed to the rod from above the spring holder, and the coil spring is sandwiched between the spring holder and the frame by tightening the nut. Accordingly, the frame can be shifted in the vertical direction with respect to the load sensor.

Effect of the Invention

In accordance with the present invention, the frame can be shifted in the vertical direction with respect to the load sensor. Accordingly, even if the lower rail, the upper rail, the frame and the like are distorted during the assembling or the like, an initial load generated by such distortions can be prevented from being applied to the load sensor.

Moreover, the coil spring is sandwiched between the frame and the spring holder in a state of being compressed by tightening the nut. Accordingly, the load sensor is fixed to the frame more stably and appropriately. Therefore, it becomes easier to assemble the passenger's weight measurement device.

Furthermore, the load is stably applied from the coil spring to the nut owing to elastic deformation of the coil spring, which is caused by tightening the nut.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 This is a perspective diagram of a passenger's weight measurement device 1 for a vehicle seat.

FIG. 2 This is an exploded perspective diagram of the passenger's weight measurement device 1.

FIG. 3 This is a perspective diagram of a load sensor 21.

FIG. 4 This is a plan diagram of a rectangular frame 30.

FIG. 5 This is a plan diagram of a right front portion of the rectangular frame 30.

FIG. 6 This is a cross-sectional diagram showing a cross section along a section line VI-VI of FIG. 5.

FIG. 7 This is a cross-sectional diagram showing a cross section along a section line VII-VII of FIG. 5.

FIG. 8 This is a cross-sectional diagram showing a modification example of FIG. 6, and showing a cross section along the section line VI-VI in a similar way to FIG. 6.

FIG. 9 This is a cross-sectional diagram showing a modification example of FIG. 7, and showing a cross section along the section line VII-VII in a similar way to FIG. 7.

BEST MODE FOR CARRYING OUT THE INVENTION

A best mode for carrying out the present invention will be described below by using the drawings. On embodiments to be described below, a variety of technically preferable limitations are imposed in order to carry out the present invention; however, the scope of the invention is not limited to the following embodiments and illustrated examples.

FIG. 1 is a perspective diagram of a passenger's weight measurement device 1 for a vehicle seat, and FIG. 2 is an exploded perspective diagram of the passenger's weight measurement device 1.

As shown in FIG. 1 and FIG. 2, a slide adjuster 2 for adjusting a back-and-forth position of the vehicle seat is attached onto a floor of a passenger's room. The slide adjuster 2 includes a left and right pair of lower rails 3 provided in parallel to each other, a left and right pair of upper rails 4 engaged with the lower rails 3 so as to be capable of sliding on the respective lower rails 3 in a rear and front direction with respect to the lower rails 3, a lower bracket 5 fixed to lower surfaces of the lower rails 3 by bolt/nut coupling or rivet coupling and bridged between the left and right lower rails 3, a lock mechanism 6 for locking the upper rails 4 to the lower rails 3 and for releasing the locking, brackets 7 attached onto front end portions of the lower surfaces of the respective lower rails 3, and brackets 8 attached onto rear end portions of the lower surfaces of the respective lower rails 3. These brackets 7 and 8 are attached onto the vehicle floor, and the lower rails 3 are fixed to the vehicle floor.

Brackets 9 are fixed to middle positions of upper surfaces of the respective upper rails 4 in a rear and front direction by the bolt/nut coupling or the rivet coupling. The brackets 9 are provided in a state of being erected with respect to upper surfaces of the upper rails 4. A right end portion of a submarine pipe 10 is welded to the brackets 9, and the submarine pipe 10 is bridged between the two left and right brackets 9.

A load sensor 21 is mounted on a front end portion of the upper surface of the right upper rail 4, and another load sensor 21 is mounted on a rear end portion thereof. Also on the upper surface of the left upper rail 4, load sensors 21 are mounted on a front end portion and rear end portion thereof, respectively. When viewed from the above, these four load sensors 21 are arranged so as to be apexes of a square or a rectangle.

FIG. 3 is a perspective diagram of the load sensor 21. All of the load sensors 21 are provided in a similar way. As shown in FIG. 3, the load sensor 21 includes a columnar sensing portion 21 a that senses a load, a plate-like flange portion 21 b extending horizontally in a rear and front direction from a lower end of the sensing portion 21 a, a rod 21 c extending upward from an upper end of the sensing portion 21 a, and a connector 21 d extending from the sensing portion 21 a so as to be parallel to the flange portion 21 b. The rod 21 c is formed into a male screw shape. Female screw-shaped circular holes 21 e and 21 f which penetrate the flange portion 21 b in the vertical direction are formed in front and rear portions of the flange portion 21 b, respectively. The sensing portion 21 a incorporates a strain gauge therein, and the load is converted into an electric signal by the strain gauge.

As shown in FIG. 2, the load sensor 21 is fixed to the right upper rail 4. Specifically, a lower surface of the flange portion 21 b abuts on the upper surface of the upper rail 4, and two bolts 22 inserted through the upper rail 4 upward from below are screwed to the circular holes 21 e and 21 f, respectively. Therefore, the load sensor 21 is fixed. Note that the load sensor 21 may be fixed to the upper rail 4 by fastening nuts to the bolts 22 on the flange portion 21 b without forming any screw threads in the circular holes 21 e and 21 f.

Any load sensor 21 is fixed to the upper rails 4 as described above. However, with regard to the two load sensors 21 fixed to the rear portions thereof, the connectors 21 d are directed forward, and with regard to the two load sensors 21 fixed to the front portions thereof, the connectors 21 d are directed backward.

As shown in FIG. 1 and FIG. 2, the frame 30 having a rectangular frame shape is mounted on these four load sensors 21. FIG. 4 is a top diagram of the rectangular frame 30. As shown in FIG. 4, the rectangular frame 30 is composed of a left and right pair of beams 31, a front beam 32, and a rear cross pipe 33.

Either of the beams 31 is a metal member having a U-shaped cross section, and has a web 31 a, an inner flange 31 b, and an outer flange 31 c. Attachment holes 31 d are formed in a front portion and a rear portion of the web 31 a, respectively.

The front beam 32 is a metal member having a U-shaped cross section, and has a web 32 a, a front flange 32 b, and a rear flange 32 c. The front beam 32 is bridged between front end portions of the left and right beams 31, and is welded to these beams 31.

The cross pipe 33 is bridged between rear end portions of the left and right beams 31, and is welded to these beams 31.

The rods 21 c of the load sensors 21 are inserted into the respective attachment holes 21 d upward from below, and nuts 46 are screwed to the rods 21 c. Therefore, the load sensors 21 are attached onto a right front portion, a right rear portion, a left front portion and a left rear portion of the rectangular frame 30, respectively. Referring to FIG. 5 to FIG. 7, an attachment structure for attaching the right front load sensor 21 onto the right front portion of the rectangular frame 30 will be described. FIG. 5 is a plan diagram of the right front portion of the rectangular frame 30, FIG. 6 is a cross-sectional diagram showing a cross section along a line VI-VI, and FIG. 7 is a cross-sectional diagram showing a cross section along a line VII-VII. As shown in FIG. 5 to FIG. 7, an annular bush 41 is fitted to an edge of the right front attachment hole 31 d, and grease is applied on the bush 41, The bush 41 is an oilless bush formed by impregnating oil into a metal material, or is made of synthetic resin. The bush 41 may be one made of other materials. Moreover, a stepped collar 42 composed of a cylindrical portion 42 a and an annular plate-like flange portion 42 b formed on one end surface of the cylindrical portion 42 a is inserted through the attachment hole 31 d in an inside of the bush 41. Here, the cylindrical portion 42 a is inserted through the attachment hole 31 d upward from below, and the flange portion 42 b engages with a lower surface of the web 31 a via the bush 41. Therefore, the stepped collar 42 is not pulled out upward. Moreover, the cylindrical portion 42 a protrudes from an upper surface of the web 31 a, and an upper end surface of the cylindrical portion 42 a is located at a higher position than the upper surface of the web 31 a. Here, the cylindrical portion 42 a is fitted to the bush 41, and there is no gap between the cylindrical portion 42 a and the bush 41.

The rod 21 c of the load sensor 21 is inserted through the stepped collar 42 upward from below. An inner diameter of the stepped collar 42 is designed to be slightly larger than a diameter of the rod 21 c, and by such designing, a dimension error and an attachment position error are solved.

The nut 46 is screwed to the rod 21 c. A plain washer 43, a coil spring 44 and a spring holder 45 are interposed between the upper surface of the web 31 a of the beam 31 and the nut 46. The rod 21 c and the cylindrical portion 42 a of the stepped collar 42 are inserted through the plain washer 43, and the plain washer 43 is set in a state of being mounted on the web 31 a, and particularly, on the bush 41. Furthermore, the rod 21 c is inserted through the coil spring 44, and the coil spring 44 is set in a state of being mounted on the plain washer 43. A portion of the coil spring 44, which is brought into contact with the plain washer 43, is formed to be flat.

The spring holder 45 includes a cup portion 45 c in which a through hole is formed in a bottom 45 b, and an annular flange 45 a formed on an outer circumferential surface in an opening of the cup portion 45 c. Then, the rod 21 c penetrates through the through hole of the bottom 45 b of the cup portion 45 c, the bottom 45 b of the cup portion 45 c is set in a state of being mounted on an end surface of the stepped collar 42, and the cup portion 45 c is inserted into the coil spring 44. Moreover, the coil spring 44 and the plain washer 43 are set in a state of being sandwiched between the flange 45 a of the spring holder 45 and the web 31 a.

The nut 46 is screwed to the rod 21 c in a state of being inserted into the cup portion 45 c, and by tightening the nut 46, the bottom 45 b of the cup portion 45 c is sandwiched between the nut 46 and the upper end surface of the cylindrical portion 42 a, and the coil spring 44 and the plain washer 43 are sandwiched between the flange 45 a and the web 31 a of the beam 31. Moreover, since the coil spring 44 is compressed by tightening the nut 46, the load is applied to the nut 46, and accordingly, the nut 46 is prevented from being loosened. Note that the coil spring 44 is set in a state of being mounted on the web 31 a of the beam 31 via the plain washer 43. However, the coil spring 44 may be set in a state of being directly mounted on the web 31 a of the beam 31, and the coil spring 44 may be sandwiched between the flange 45 a and the web 31 a.

Like the right front load sensor 21, the left front, left rear and right rear load sensors 21 are attached onto the left front, left rear and right rear attachment holes 31 d, respectively. In a state where the four load sensors 21 are attached onto the rectangular frame 30, the submarine pipe 10 is located behind the front beam 32.

As shown in FIG. 1 and FIG. 2, side frames 51 are welded to the outer flanges 31 c of the left and right beams 31, respectively. These side frames 51 are parts of a bottom frame of the vehicle seat. As best shown in FIG. 2, a lower portion 52 of the side frames 51 may constitute a concave part opening downward.

From above, front portions of the side frames 51 are covered with a pan frame 53, and the side frames 51 and the pan frame 53 are fixed to each other by the bolt/nut coupling or the rivet coupling. A seat spring 54 is bridged between the cross pipe 33 and the pan frame 53, a cushion is mounted on the pan frame 53 and the seat spring 54, and the cushion, the pan frame 53 and the side frames 51 are entirely covered with a cover.

A backrest frame is coupled to rear ends of the side frames 51, and is capable of rising and falling by a reclining mechanism. Note that the backrest frame and the cushion are not shown in order to make it easy to view the drawings.

In the passenger's weight measurement device 1 configured as described above, when a passenger is seated on a seat bottom, a weight of the passenger is applied to the four load sensors 21 through the rectangular frame 30, and is converted into electric signals by these load sensors 21.

Here, the load sensors 21 are attached between the upper rails 4 and the rectangular frame 30, and the load sensors 21 move in a rear and front direction integrally with the vehicle seat. Accordingly, a load inputted from the vehicle seat to the load sensors 21 can be always kept constant irrespective of position of the vehicle seat in a rear and front direction. Therefore, measuring accuracy of the passenger's weight can be enhanced.

Moreover, the spring holder 45 is mounted on the upper end surface of the stepped collar 42, and the coil spring 44 is sandwiched between the spring holder 45 and the web 31 a by tightening the nut 46. Accordingly, the rectangular frame 30 can be shifted in the vertical direction with respect to the load sensors 21. Therefore, noise of the load generated by distortion of the slide adjuster 2 and the like becomes smaller.

Moreover, even if the rectangular frame 30 can be shifted in the vertical direction with respect to the load sensors 21, the coil springs 44 are interposed between the nuts 46 and the webs 31 a, and accordingly, the load sensors 21 can be fixed to the rectangular frame 30 more stably and appropriately. Therefore, it becomes easier to assemble the passenger's weight measurement device 1.

Moreover, the load is stably applied from each of the coil springs 44 to each of the nuts 46 owing to elastic deformation of the coil spring 44, which is caused by tightening the nut 46.

Moreover, the submarine pipe 10 is located behind the front beam 32, and accordingly, when forward inertial force is applied to the passenger owing to a frontal collision or the like of the vehicle, buttocks of the passenger seated on the vehicle seat are restrained by the submarine pipe 10. Therefore, a so-called submarine phenomenon in which the passenger moves under a waist belt can be prevented.

Note that the present invention is not limited to the above-described embodiment, and various improvements and design changes can be made within the scope without departing from the gist of the present invention.

In the above-described embodiment, the coil spring 44 is set in the state of being mounted on the plain washer 43, and the portion of the coil spring 44, which is brought into contact with the plain washer 43, is made flat. However, for example as shown in FIG. 8 and FIG. 9, a washer 431 in which an inner portion thereof is formed as a protruding portion 431 a protruding upward, may be used. An outer edge portion of the protruding portion 431 a is formed into a curved surface, and a step difference 431 b formed by the protruding portion 431 a is formed on an upper surface of the washer 431. An end portion of the coil spring 44 is set in a state of being engaged with the step difference 431 b, and the coil spring 44 abuts on the curved surface of the protruding portion 431 a and a flat surface of the washer 431. Therefore, the coil spring 44 is centered by the protruding portion 431 a of the washer 431 so as not to slip on the flat surface of the washer 431. 

What is claimed is:
 1. A vehicle seat, comprising: a load sensor configured to measure a load applied from an occupant, the load sensor having a rod extending therefrom; a seat cushion frame comprising right and left side frames that extend along a front-rear axis; and a bracket member attaching the load sensor to at least one of the right and left side frames, the bracket member being secured to a side of the at least one side frame that faces toward a center of the vehicle seat, wherein a lower surface of the at least one side frame has a concave part opening downward, at least a part of the load sensor is lower than the concave part, and the load sensor is closer to the center of the vehicle seat than the concave part.
 2. The vehicle seat as claimed in claim 1, wherein a same horizontal plane intersects the concave part and the bracket member.
 3. The vehicle seat as claimed in claim 1, wherein the load sensor includes a connector, and the connector is lower than the concave part.
 4. The vehicle seat as claimed in claim 1, wherein the bracket member includes a sectional U-shaped part, and at least a part of the load sensor is in a space within the sectional U-shaped part.
 5. The vehicle seat as claimed in claim 4, wherein the rod is in the space within the sectional U-shaped part.
 6. The vehicle seat as claimed in claim 1, further comprising: lower rail members configured to be attached to a vehicle; upper rail members that are slideable with respect to the lower rail members; and first and second fastening units attaching the load sensor to at least one of the upper rail members, wherein the first fastening unit and the second fastening unit are lower than the concave part.
 7. The vehicle seat as claimed in claim 1, further comprising: lower rail members configured to be attached to a vehicle; upper rail members that are slideable with respect to the lower rail members; and first and second fastening units attaching the load sensor to at least one of the upper rail members, wherein at least a part of the rod is between the first fastening unit and the second fastening unit, the first fastening unit and the second fastening unit being in tandem.
 8. A vehicle seat, comprising: a load sensor configured to measure a load applied from an occupant, the load sensor having a rod extending therefrom; lower rail members configured to be attached to a vehicle; upper rail members that are slideable with respect to the lower rail members; a seat cushion frame comprising right and left side frames that extend along a front-rear axis; and a bracket member attaching the load sensor to at least one of the right and left side frames, the bracket member being secured to a side of the at least one side frame that faces toward a center of the vehicle seat, wherein a lower surface of the at least one side frame has a curved concave part opening downward, at least a part of the load sensor is lower than the curved concave part, and the load sensor is closer to the center of the vehicle seat than the curved concave part.
 9. The vehicle seat as claimed in claim 8, wherein a same horizontal plane intersects the curved concave part and the bracket member.
 10. The vehicle seat as claimed in claim 8, wherein the load sensor includes a connector, and the connector is lower than the curved concave part.
 11. The vehicle seat as claimed in claim 8, wherein the bracket member includes a sectional U-shaped part, and at least a part of the load sensor is in a space within the sectional U-shaped part.
 12. The vehicle seat as claimed in claim 11, wherein the rod is in the space within the sectional U-shaped part.
 13. The vehicle seat as claimed in claim 8, wherein first and second fastening units attach the load sensor to at least one of the upper rail members, and the first fastening unit and the second fastening unit are lower than the curved concave part.
 14. The vehicle seat as claimed in claim 8, wherein first and second fastening units attach the load sensor to at least one of the upper rail members, and at least a part of the rod is between the first fastening unit and the second fastening unit, the first fastening unit and the second fastening unit being in tandem.
 15. A vehicle seat, comprising: a load sensor configured to measure a load applied from an occupant, the load sensor having a rod extending therefrom; lower rail members configured to be attached to a vehicle; upper rail members that are slideable with respect to the lower rail members; a seat cushion frame comprising right and left side frames that extend along a front-rear axis; and a bracket member attaching the load sensor to at least one of the right and left side frames, the bracket member being secured to a side of the at least one side frame that faces toward a center of the vehicle seat, wherein a lower surface of the at least one side frame has a concave part opening downward, the load sensor is closer to the center of the vehicle seat than the concave part and an outer edge of the at least one side frame, and a same horizontal plane intersects the load sensor and the concave part.
 16. The vehicle seat as claimed in claim 15, wherein the load sensor includes a connector, and the connector is lower than the concave part.
 17. The vehicle seat as claimed in claim 15, wherein the bracket member includes a sectional U-shaped part, and at least a part of the load sensor is in a space within the sectional U-shaped part.
 18. The vehicle seat as claimed in claim 17, wherein the rod is in the space within the sectional U-shaped part.
 19. The vehicle seat as claimed in claim 15, wherein first and second fastening members attach the load sensor to at least one of the upper rail members, and the first fastening member and the second fastening member are lower than the concave part.
 20. The vehicle seat as claimed in claim 15, wherein first and second fastening members attach the load sensor to at least one of the upper rail members, and at least a part of the rod is between the first fastening member and the second fastening member, the first fastening member and the second fastening member being in tandem.
 21. The vehicle seat as claimed in claim 1, further comprising a connecting member that connects rear parts of the right and left side frames, wherein the load sensor includes a connector, the rod is between the connecting member and a tip of the connector, and a same vertical plane intersects the concave part and the rod.
 22. The vehicle seat as claimed in claim 8, further comprising a connecting member that connects rear parts of the right and left side frames, wherein the load sensor includes a connector, the rod is between the connecting member and a tip of the connector, and a same vertical plane intersects the curved concave part and the rod.
 23. The vehicle seat as claimed in claim 15, further comprising a connecting member that connects rear parts of the right and left side frames, wherein the load sensor includes a connector, the rod is between the connecting member and a tip of the connector, and a same vertical plane intersects the concave part and the rod.
 24. A method of using a vehicle seat, the method comprising: fixing the vehicle seat as claimed in claim 1 to a vehicle.
 25. A method of using a vehicle seat, the method comprising: fixing the vehicle seat as claimed in claim 1 to the vehicle.
 26. A method of using a vehicle seat, the method comprising: fixing the vehicle seat as claimed in claim 15 to the vehicle.
 27. A method of assembling a vehicle seat that comprises a seat cushion frame comprising right and left side frames that extend along a front-rear axis, the method comprising: attaching, to at least one of the right and left side frames, by way of a bracket member secured to a side of the at least one side frame that faces toward a center of the vehicle seat, a load sensor that is configured to measure a load applied from an occupant of the vehicle seat and that has a rod extending therefrom so that at least a part of the load sensor is lower than a concave part opening downward of a lower surface of the at least one side frame and so that the load sensor is closer to the center of the vehicle seat than the concave part.
 28. The method as claimed in claim 27, further comprising: attaching upper rail members to lower rail members that are configured to be attached to a vehicle so that the upper rail members are slideable with respect to the lower rail members.
 29. The method as claimed in claim 27, further comprising: attaching upper rail members to lower rail members that are configured to be attached to a vehicle so that the upper rail members are slideable with respect to the lower rail members, wherein the load sensor is attached to the at least one side frame so that (1) the load sensor is closer to the center of the vehicle seat than an outer edge of the at least one side frame and so that (2) a same horizontal plane intersects the load sensor and the concave part opening downward of the lower surface of the at least one side frame.
 30. The vehicle seat as claimed in claim 1, wherein the concave part slopes upward or downward in the forward or rear direction so as to open downward.
 31. The vehicle seat as claimed in claim 8, wherein the curved concave part slopes upward or downward in the forward or rear direction so as to open downward.
 32. The vehicle seat as claimed in claim 15, wherein the concave part slopes upward or downward in the forward or rear direction so as to open downward.
 33. The method as claimed in claim 27, wherein the concave part slopes upward or downward in the forward or rear direction so as to open downward.
 34. A vehicle seat, comprising: a load sensor configured to measure a load applied from an occupant, the load sensor having a rod extending therefrom; a seat cushion frame comprising right and left side frames that extend along a front-rear axis; and a bracket member attaching the load sensor to at least one of the right and left side frames, the bracket member being secured to a side of the at least one side frame that faces and a cutter of the vehicle seat, wherein a lower surface of the at least one side frame has a concave part that slopes upward or downward in the forward or rear direction so as to open downward, and at least a part of the load sensor is lower than the concave part.
 35. The vehicle seat as claimed in claim 1, wherein the rod of the load sensor extends in a direction substantially parallel to an up-down axis of the vehicle seat.
 36. The vehicle seat as claimed in claim 8, wherein the rod of the load sensor extends in a direction substantially parallel to an up-down axis of the vehicle seat.
 37. The vehicle seat as claimed in claim 15, wherein the rod of the load sensor extends in a direction substantially parallel to an up-down axis of the vehicle seat.
 38. The method as claimed in claim 27, wherein the load sensor is attached so that the rod of the load sensor extends in a direction substantially parallel to an up-down axis of the vehicle seat.
 39. The vehicle seat as claimed in claim 14, wherein the rod of the load sensor extends in a direction substantially parallel to an up-down axis of the vehicle seat. 